From: Eric Neilsen (e.neilsen@worldnet.att.net)
Date: 04/09/03-09:44:38 PM Z
Manuel,
Because you have not read all that has been written on this. Ted Rice
in Santa Fe was the first printer that I knew that did just that. Every
time you open a bottle of Ferric Oxalate with the Pot Chlorate added to
it, you can smell the small release of chlorine. The bottle loses its
ability to adjust contrast upward. You can mix fresh batches of a
potassium chlorate solution each time you print. The hard part about
this approach is that it only requires a small amount to have an effect
that an accurate measurement may prove too difficult for many.
Eric Neilsen Photography
4101 Commerce Street
Suite 9
Dallas, TX 75226
http://e.neilsen.home.att.net
http://ericneilsenphotography.com
-----Original Message-----
From: Manuel Gomes Teixeira [mailto:punctumgt@netvisao.pt]
Sent: Wednesday, April 09, 2003 6:40 PM
To: alt-photo-process-l@sask.usask.ca
Subject: Re: hp and pot di with pt/pd
Kerik,
Tomorrow I'm going to order Na2 for the first time from B&S.
It will be interesting and useful for all of us to hear some more
details
of your and others experiences with this method of contrast control
in
Pt/Pd printing.
I suppose that you use NA2 in substitution of K2PtCl4 when printing
with
the classic Pt/Pd approach. Is that so ? Or is there any other more
complex procedures advised ?
Until now I've had better results with H2O2 added to the sensitiser
solution than with Potassium Chlorate.
My last question for today:
Why in all Pt/Pd literature is never advised to use Potassium Chlorate
solution added to the sensitiser as H2O2 and instead is added
previously to
the Ferric Oxalate solution ? Is there any chemical explanation for
that ?
Thanks for your time ! :-)
Kindest regards from Portugal
Manuel Gomes Teixeira
Punctum Studios
Aveiro
Portugal
> From: Kerik <Kerik@kerik.com>
> Reply-To: alt-photo-process-l@sask.usask.ca
> Date: Wed, 09 Apr 2003 11:09:12 -0700
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: hp and pot di with pt/pd
>
> Christina,
>
> HP in the developer will increase contrast somewhat, as others have
stated.
> However, I really don't recommend this approach. The HP is quite
unstable
> and the developer contrast character will likely change during the
course
> of a single printing session. Enough to drive you nuts and waste time
and
> materials.
>
> Sodium dichromate is more commonly used as a developer additive rather
than
> potassium, although I would think potassium would provide similar
effects
> if you balance the quantity of the dichromate relative to sodium. I
say
> this because this approach has been standardized (by Phil Davis, I
believe)
> based on a drop count of 50% sodium dichromate solution per a given
volume
> of potassium oxalate. If you were to use potassium, I believe you
would
> have to use more of it since it will only exist in solution at a
> concentration of about 11%.
>
> And finally, if you haven't already, I really recommend experimenting
with
> B&S's "Na2" contrast agent which is added to the sensitizer rather
than the
> developer. It gives you a much wider range of contrast adjustment than
> available with the dichromate approach, and it doesn't cause the
> degredation of print quality associated with the "Ferric Oxalate No.
2"
> approach that causes so many people problems when the are starting
with
> this process.
>
> Kerik www.Kerik.com
>
>> Good morning!
>> Does anyone use either hydrogen peroxide or potassium dichromate
added
>> to the developer or hp added to the sensitizer (the latter not for
>> palladium)?
>> Correct me if I am wrong here: added to the developer, dichromate
will
>> increase contrast? And hp will decrease contrast? Why does this
happen?
>> Chris
>
>
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